Posterior MI and Large R in V1

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Elias Hanna, MD

Posterior Infarction:

-When accompanied by inferior or lateral STEMI, posterior infarction is easily recognized, but it can be difficult to diagnose when it occurs alone, the so-called true posterior STEMI.

-ST-segment depression that is most prominent in any of the leads V1 through V3 often indicates posterior STEMI rather than non–ST-elevation ACS and indicates the need for emergency reperfusion.

-On the other hand, ST-segment depression that is greatest in leads other than V1-V3 is more indicative of diffuse subendocardial ischemia (non-ST-elevation ACS).

-If a patient has persistent true angina and ST-segment depression in leads V1-V3, record leads V7-V9 to confirm the dg and perform emergent reperfusion (thrombolysis or PCI).

V7-V9 will have ST-segment elevation and possibly Q waves.

Also, if a patient has persistent angina and a non-diagnostic ECG, record leads V7-

V9. ST-segment elevation in those leads may be the only ECG indicator of ischemia

(usually LCx ischemia).

-Large and/or wide R wave in leads V1 or V2 supports the dg of posterior infarction but is only seen in ~50% of the cases. Large R is reciprocal to posterior Q in this context.

Causes of large R wave in V1 or V2:

Diagnosis

RVH

Confirmatory clues

Right axis deviation

Right atrial enlargement

ST depression and T inversion in V1-V2

RBBB

Posterior MI

QRS wide> 120 msec (>100 msec if incomplete RBBB)

ST depression in V1-V3 but T upright (≠RVH)

ST elevation and/or Q waves in V7-V9

WPW Short PR, delta wave, widened QRS

Normal variant Large R wave in V1-V2 is the only abnormality on ECG

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